[A comparative study on the diagnostic value of ¹⁸F-PSMA PET/CT PRIMARY score and PSMA expression score for...

Objective: To compare the diagnostic value of fluorine 18-labelled prostate-specific membrane antigen (PSMA) PET/CT PRIMARY score and PSMA expression score for clinically significant prostate cancer (csPCa). Methods: The data of 70 patients with prostate cancer who underwent radical prostatectomy at Beijing Hospital from February 1, 2019 to February 29, 2024 were retrospectively analyzed. All patients underwent whole body ¹⁸F-PSMA PET/CT examination before surgery and pathological large sections of prostate specimens were made after surgery. According to the pathological section results, the lesions were divided into csPCa group (Gleason scores≥7) and non-csPCa group (Gleason scores=6 or benign). The PRIMARY score and PSMA expression score were used to evaluate prostatic lesions on PSMA PET/CT images, respectively. The differences in PRIMARY score, PSMA expression score, maximum standardized uptake value (SUV_max), lesion-to-background ratios (LBR), PSMA uptake characteristics, and location distribution were compared between csPCa group and non-csPCa group. Multivariate logistic regression analysis was performed to determine the correlation factors for the incidence of csPCa. By plotting the receiver operator characteristic (ROC) curve and calculating the area under the curve (AUC), the optimal diagnostic threshold for csPCa of each factor was determined. The differences in AUC were compared using the Delong test. Quantitative data was represented as M (Q₁, Q₃). Results: The 70 patients aged 70 (64, 75) years with a total of 108 lesions, including 83 lesions (76.9%) in the csPCa group and 25 lesions (23.1%) in the non-csPCa group. There were differences between csPCa group and non-csPCa group in PRIMARY score [4 (3, 5) vs 2 (1, 4)], PSMA expression score [2 (2, 2) vs 1 (1, 2)], SUV_max [9.10 (5.70, 15.80) vs 5.40 (3.35, 6.90)], LBR [2.86 (2.09, 4.53) vs 1.96 (1.42, 2.58)], and proportion of focal uptake patterns [74.7% (62/83) vs 32.0% (8/25)] (all P<0.05). There was no statistically significant difference in the location distribution between the two groups (P>0.05). Multivariate logistic regression analysis indicated the higher the PRIMARY score, the higher the risk of developing csPCa (OR=1.863, 95%CI: 1.360-2.552). ROC curves revealed that the AUCs of the PRIMARY score and PSMA expression score for csPCa were 0.751 (95%CI: 0.659-0.829) and 0.697 (95%CI: 0.601-0.781), respectively, without statistically difference (Z=1.438, P>0.05). The cut-off values for diagnosing csPCa were 3 score for PRIMARY score and 2 score for PSMA expression score, respectively. Conclusions: The higher the ¹⁸F-PSMA PET/CT PRIMARY score, the higher the risk of developing csPCa. The PRIMARY score has good diagnostic efficacy for csPCa.